Because udev sucks, it is bloated and overengineered. udev is just like systemd, it locks you into using non-portable crap that you can't avoid because multiple programs depend on it. Look, even FreeBSD was forced to rewrite[0] this crappy library because libinput hard-depends on udev. Without libinput you can't use wayland and many other cool stuff.

Michael Forney (author of cproc, samurai, Oasis Linux, ...) decided to fork[1] libinput and remove the hard dependency on udev. However, this fork has a drawback that requires patching applications to use libinput_netlink instead of the libinput_udev API in order to use the automatic detection of input devices and hotplugging. Static configuration is also required for anything other than input devices (e.g drm devices).

Thankfully udev has stable API and hopefully no changes will be made to it the future. On this basis I decided to create this clean-room implementation of libudev which can be used with any or without a device manager.

[0] https://github.com/FreeBSDDesktop/libudev-devd
[1] https://github.com/oasislinux/libinput

What Works

xorg-server
dosfstools - need to implement udev_enumerate_add_match_parent()
libinput
usbutils
wlroots
weston
libusb
kwin
???

Dependencies

C99 compiler (build time)
POSIX make (build time)
POSIX & XSI libc
Linux >= 2.6.39

Installation

make
make PREFIX=/usr install

Hotplugging

Note that hotplugging support is fully optional. You can skip this step if you don't have a need for the hotplugging capability.

If you're using mdev-like device manager, refer to mdev.conf for config example.

If you're using other device manager, you need to configure it to rebroadcast kernel uevents. You can do this by either patching(see below) device manager or simply executing helper.c for each uevent.

If you're developing your own device manager, you need to rebroadcast kernel uevents to 0x4 netlink group of NETLINK_KOBJECT_UEVENT. This is required because libudev-zero can't simply listen to kernel uevents due to potential race conditions. Refer(but don't copy blindly) to helper.c for example how it could be implemented in C.

Don't hesitate to ask me everything you don't understand. I'm usually hanging around in #kisslinux at libera.chat, but you can also email me or open an issue here.

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Thank you very much!